In many machining operations, an aqueous coolant is sprayed or flowed at the location where a cutting tool engages the workpiece, for lubrication and cooling purposes. The coolant is then collected in a tank located below the machine and recycled for continuous use for as long as possible.
Aqueous coolants of this type are fairly expensive, so it is advantageous to maintain such aqueous coolants in usable condition for as long as possible. Typical machining operations also include lubricating oil for lubricating movable parts. Eventually, this oil drips or flows into the aqueous coolant tank, where it floats upon the surface of the aqueous coolant due to its lighter weight and lower density. This oil, referred to as "tramp oil," will eventually also contribute to bacterial growth within the aqueous coolant, resulting in a foul odor and reducing the useful life of the aqueous coolant.
Due to environmental concerns, the oil-contaminated aqueous coolant must be treated as hazardous waste, and therefore represents an environmental and economic concern. Thus, tramp oil represents a serious environmental and economic problem with respect to maintaining proper and cost effective aqueous coolant use during machining operations.
A number of skimming devices have been developed over the years to remove tramp oil from the surface of aqueous coolant in a coolant tank for a machine. Disk skimmers include a disk which extends into the aqueous coolant and into contact with the tramp oil. Rotation of the disk near the surface results in removal of some oil from the surface, whereupon it is scraped by a blade and removed. Belt type skimmers involve an endless belt which removes tramp oil from the surface of the aqueous coolant, whereupon it is also scraped therefrom for removal. Disk and belt skimmers of this type are relatively inefficient and have space limitations for proper mounting and operation.
Floating tube skimmers and weir-type skimmers adapt to liquid level fluctuations, and they generally include a pump for pumping the skimmed liquid to a separation device. Such skimmers have proved to be acceptable in relatively large bodies such as lakes, ponds, rivers or even oceans. However, their size typically prevents their use in machining applications. In machining operations, most coolant tanks are as shallow as five or six inches, or as deep as 14 to 16 inches. Also, some machining coolant tanks are located in relatively inaccessible places without much spare space located adjacent thereto.
Weir-type skimmers also have the disadvantage of being too large to be readily adapted for machining operations. With floating tube or weir-type skimmers, liquid is retrieved from the tank via a suction line operatively connected to a suction pump. For most operations of this type, a positive displacement pump provides this suction force. Because the liquid removed from the tank includes a mixture of two different liquid components, and the proportions of these two liquid components vary over a period of use, the volume pulled by the pump is subject to variation. These volume variations can adversely affect the efficient operation of the pump and the entire system. Thus, while these relatively large size skimming devices have proved effective in their specific environment, i.e. large bodies of water, they suffer from some disadvantages which would be aggravated if the devices were to be adapted for use in relatively small coolant tanks.
In summary, in machining operations it is necessary to skim primarily tramp oil from the surface of the aqueous coolant in the tank (though the skimmed liquid will also include some coolant), to deliver the tramp oil coolant mixture to a separation unit, to separate the tramp oil from the aqueous coolant for collection, and to return the aqueous coolant to the tank for reuse.
One system which accomplishes this is disclosed in both U.S. Pat. No. 5,601,705 and U.S. patent application Ser. No. 08/644,920 (now abandoned) which are both hereby fully incorporated by reference. One component of the system disclosed in these documents is a coalescer having an outer housing with an entry port and an exit port and a flow path therebetween. The aqueous coolant contaminated with tramp oil is pumped through the entry port of the coalescer, passes through the coalescer in which the tramp oil is removed, the cleansed coolant exiting the exit port of the coalescer. Inside the housing, a plurality of baffles define the flow path of the aqueous coolant. Due to the lower specific gravity of the tramp oil relative to the aqueous coolant, the tramp oil rises through a hollow fitting located above the first exit port and exits via an outlet where it is collected.
One difficulty with the coalescer disclosed in applicant's abandoned patent application Ser. No. 08/644,920 is that dirt accumulates in the coalescing tank after several months. A sludge drain may be installed on the bottom of the coalescing tank which allows dirt on the bottom of the tank to drain out. However, not all the dirt drains out because dirt builds up between the plates. Dirt and other contaminates which build up on the plates are not easily removed by simply opening the drain plug. Because the coalescer is a sealed single unit, cleaning of the plates is difficult and requires a great deal of time and effort because the plates are neither visible nor accessible. Applicant's present invention allows for quick and easy removal of the plates and easy access for cleaning the plates.
Thus, it is an object of the present invention to provide a coalescer having parallel plates which are removable and may be quickly and easily cleaned for proper operation of the coalescer.
It is another object of the present invention to provide a coalescer which may be quickly and easily flushed of sludge or dirt which accumulates on the bottom of the coalescer.
It is another object of the present invention to provide a coalescer which has a removable cartridge which may be quickly and accurately fixed in a specific location so as to cause the coalescer as a unit to operate properly.
It is a further object of this invention to optimize the useful life of aqueous coolant used in conjunction with the operation of a machine tool. As a corollary, it is also an object of this invention to minimize the bacteria formation and hazardous waste conditions created by tramp oil contamination of such aqueous coolant.